This invention relates generally to hot-air ovens for reheating packages containing pre-cooked food initially in a cold or frozen state, and more particularly to a counter-top unit of this type which is useable in homes and offices and is adapted rapidly to reheat a stack of such packages to a service temperature level and to maintain the food at this level for an indefinite period.
To satisfy the growing need for quickly prepared inexpensive meals, convenience food systems have been developed in which the meals to be later served are first cooked, packaged, and then deep-freezed. When one wishes to eat a particular meal, the selected package is taken out of the freezer and the frozen pre-cooked meal is then thawed and reheated. Typical of such operations is the so-called TV dinner in which a pre-cooked meal in the frozen state is sealed within a serving tray. The dinner is kept in the freezer until there is a demand for it, at which point the TV dinner is thawed and reheated in a microwave oven, a convection oven or whatever heater is available. The term "packages" as used herein is intended to cover any sealed dish, tray, pouch or other hard or soft container having pre-cooked food therein.
In reheating a pre-cooked frozen meal in homes and offices, it is difficult when going from the frozen state to a service level in a conventional hot air oven, to avoid a situation in which the core of the meal is still cold even though the outer layer is hot. When one seeks to ensure that the body of the food is hot throughout, there is a tendency to overheat the meal in the oven and thereby re-cook it, with a resultant loss in nutritional value and flavor. But even when the meal has been heated to a proper serving level, it must be served without delay, for with the typical oven it is virtually impossible to thereafter hold the meal until such time as there is a demand therefor without overheating.
For a convenience food operation to be effective, one must be able not only to reheat the pre-cooked meal to a proper service temperature level within a relatively short period, but one must be able to take into account that in a home and office, the time at which diners are ready to eat may be subject to change. Thus in a typical office having several staff members, all of whom intend to lunch at say noon, it is not at all unusual for one or more of the members to be unavailable until say an hour or so later. Existing ovens for reheating precooked frozen meals cannot cope with this common contingency.
In my copending application Ser. No. 221,208 whose entire disclosure is incorporated herein by reference, there is disclosed a counter-top unit useable in homes and offices for reheating stack of packages containing pre-cooked meals in that they are rapidly brought from the cold or frozen state to a service temperature level and thereafter maintained indefinitely at this level.
The unit disclosed in my copending application Ser. No. 221,208 includes a box-like case having telescoped therein an open-fronted inner box whose walls are spaced from those of the case to define rear and side air spaces therebetween. Mounted within the inner box is a compartment to receive a stack of packages with spacings therebetween. The perforated wall of the compartment is spaced from the rear of the inner box to define a rear plenum. In the heat-up phase, air in the rear space heated to a temperature well above the service level is blown into the plenum, the resultant pressure differential between the plenum and the rear space causing the air to flow at high velocity through the package spacings in the compartment back to the rear space to create a continuous flow loop.
Heat is provided by high-wattage and low-wattage heater elements, both of which are energized in the heat-up phase to provide the required high temperature. However, in the heat-up phase, the operation of the high-wattage element is periodically interrupted whereby the meals are then subjected to pulses of high-temperature air separated by relatively low-temperature intervals during which heat from the outer layer of food is transferred to the intermediate layers and the core thereof to prevent the outer layer from being heated above the service temperature. When the body of the meals reach the service temperature, the unit switches over to a service phase in which only the low-wattage heater element is energized and thermostatically-controlled to maintain the food at the service temperature level for an indefinite period.
A unit in accordance with the present invention acts in a similar manner, but is structurally in a less complicated form.